One of the major advantages of data processing machines is the ability to change the format in which data is presented in either visual display or printed form. Machines are controlled, using a suitable graphics control program such as the IBM Graphics Data Display Manager (GDDM) (IBM and GDDM are trade marks of the IBM Corporation), to manipulate sets of data and produce almost any form of graph (bar charts, pie charts, line graphs etc.,).
European Patent No. 26266 describes the basic operation of a graphics control program. A digital data display system in which the display device includes a plurality of random access stores into which character cell definitions are loaded from a remote central processing unit. A character cell may be a 9 x 16 picture element matrix and each is defined in the Central Processor Unit (C.P.U.) according to the requirements of a display request received from a users application program. The system control services include a graphics manager and graphics routines which construct a character buffer and character cell definition table according to the picture to be displayed. A character cell definition that is required more than once in a picture is only included once in the definition table. The character buffer having the required number of pointers to the one definition. When the character buffer and character definition table have been constructed they are transmitted to the display device using a data communication system. The system can be used for color or monochrome displays.
A class of application programs process data which generally takes the form of a two-dimensional table. Spreadsheets are a notable example. Business charting programs are another--typically a table may include a number of "sets" of values, with conceptually the same number of items in each set (though some may in fact be missing). For example, the machine may be used to plot sales of a range of products for a number of months:
______________________________________ Jan Feb Mar Apr May ______________________________________ Televisions 45 67 66 98 78 Refrigerators 19 24 67 80 Toasters 50 55 51 46 ______________________________________
Business charting programs normally have a Data Entry facility in which the display screen is formatted into uniform rows and columns of fields, into which the user can type values.
However, manual data entry is tedious and error-prone, and many users already have tabular files stored in their computer which they would prefer the charting program to use. These tabular files may be "soft" copies of printed reports, with regular columns of numbers, or they may be less formal files maintained by the user for his or her own convenience. The latter have the characteristic that the columns may be rather ragged in appearance--the human eye can distinguish the columns and recognize where values are "missing".
The problem with these tabular files for the business charting program lies in understanding the format without too much analysis (which could be time-consuming and therefore frustrating to the user). A solution which the GDDM PFG Interactive Chart Utility uses is to require the user to identify the columns of numbers, by "marking" the top-left and bottom-right positions of each column. This identification can then be saved for future use. The disadvantage is that the "marking" process is awkward to learn and use, and the identification may lose its validity if the user's columns of numbers become more ragged as he adds more numbers from day to day.